1. Field of the Invention
The present invention relates to a sealant application method wherein in the case of preliminarily applying a first sealant and next applying a second sealant to the first sealant, the adhesiveness of the second sealant to the first sealant is improved.
2. Description of the Related Art
Conventionally, application of a sealant is known to give water-tightness and air-tightness to a building or the like.
Examples of such a sealant widely used at present include a silicone sealant, MS sealant (alkoxy silicone functionalized polyoxypropylene polymer base sealant), polysulfide sealant, polyurethane sealant, acrylic urethane sealant, and acrylic sealant. A proper kind of sealant for a proper place of application is selected according to the performance of the sealants, and several kinds of the sealants are always used.
For example, in the case of a silicone sealant, it is widely used for the surrounding of a windowpane or the like owing to its excellence of weather resistance and durability. However, the outer periphery of a joint is largely contaminated with the sealant, so that actual use of the sealant is largely limited.
In the case of a modified silicone sealant, it cannot be used for the surrounding of a windowpane which requires weather resistance.
In the case of a polysulfide sealant, it is inferior to a modified silicone sealant and a silicone sealant in responsiveness to movement of a joint, so that it cannot be used for a joint of a metal curtain wall with large movement.
Thus, a proper sealant is used for a proper place according to the structure, material, etc. of a building. Accordingly, different sealants are applied to carry out successive jointing, causing a problem in adhesion.
Such application of different sealants in succession is called successive jointing of sealants. The problem in adhesion due to the successive jointing frequently arises at an actual sealant application site.
Further, in sealant modification work, a refilling process is generally carried out in such a manner that an old sealant before modification is first removed and a new sealant-is therefore filled. Also in this case, there is a problem in adhesion between the old sealant and the new sealant.
In such successive jointing of sealants, the adhesion between the sealants may become insufficient depending on the kinds of sealants, and it is therefore important to check the adhering condition at the joint.
That is, in the case of preliminarily applying a first sealant and thereafter applying a second sealant to the first sealant, a technique for improving the adhesion of the second sealant to the first sealant is required.
In the case where the first sealant is a silicone sealant, there is a difficulty in adhesion in respect of the combination of the first and second sealants used in successive jointing or modification as described in Sealant Handbook (issued by Japan Sealant Industry Association) p31 and p151. That is, in the case that the first sealant preliminarily applied is a silicone sealant, only a silicone sealant-that can adhere to the first sealant is usable as the second sealant to be next applied, and the other sealants including a modified silicone sealant, polysulfide sealant, polyurethane sealant, acrylic urethane sealant, and acrylic sealant cannot adhere to the first sealant.
Further, in the case that the first sealant is a modified silicone sealant, adhesion of a polysulfide sealant, polyurethane sealant, and acrylic urethane sealant to the first sealant is difficult.
Accordingly, it has been desired to develop a sealant application method allowing good adhesion of the second sealant to the first sealant irrespective of the kind of the first sealant.